Technical Info

This literature review was published in the Canadian Physiotherapy Orthopaedic Division Newsletter, Nov. 2016 Vol. 29, No. 4

Research Supporting the ArmLock Technique

In my first years working as a physical therapist, I found tennis elbow to be one of the most difficult and frustrating conditions to treat. Research has validated my experience that ultrasound and friction massage to the tender spot at the lateral epicondyle proved to be largely ineffective.(1,2) This literature review aims to support the rationale for a stretching technique that includes the finger extensors in the treatment of tennis elbow.

Armlock Technique

Current teachings suggest overuse of the wrist extensor, specifically Extensor Carpi Radialis Brevis (ECRB), as the primary culprit of tennis elbow.(3) The finger extensors, however, constitute up to 45% of the wrist extension moment potential.(4) EMG studies of tennis players showed that on the back hand swing, the finger extensors contracted at 80% of their maximum prior to ball contact.(5) Anatomical dissection has found the both the wrist extensor, specifically ECRB, and the finger extensors converge to form a common tendon. Any pathology associated with the wrist extensor origin would therefore have to be treated as common to both.(3) A more recent anatomical analysis analyzed thirty-nine cadaver arms and found that the index and middle finger extensor tendons converged with the wrist extensor (ECRB) at the lateral epicondyle, whereas the ring and little finger did not.(17) Therefore, a contraction of either muscle group, wrist extensor or finger extensor, independent of the other, or pathological shortening in response to repeated trauma, would increase tension on the common extensor tendon, and in the case of tennis elbow, elicit pain. A study of tennis elbow patients looked at pain on resisted extension of the middle finger (Maudsley’s test) which was found to be positive in a significant portion of the subjects with tennis elbow.(6) Their conclusion was that the finger extensors may play a greater role in tennis elbow than previously appreciated. It is time we started using this information to provide a more effective treatment for Tennis Elbow. The stretch technique presented in this review, referred to as the Armlock technique, aims to selectively stretch the finger extensors with the wrist extensors.

To simultaneously stretch the finger extensors with the wrist extensor, all the joints of the wrist and hand must be positioned into flexion. As the common extensor tendon originates proximal to the radial humeral joint, the elbow must also be held in extension with the forearm fully pronated to provide maximal elongation of the affected muscles. With the elbow and finger joints locked into their end ranges of motion, the therapist controls the amount of tension applied to the tissues with varying degrees of flexion at the wrist.

Stretching Treatment

Tennis elbow sufferers generally have a reduced extensibility of their wrist extensors.(7) Comparative research studies can provide insight as to the best method to stretch this muscle tendon complex. Results of one study showed that low load, prolonged stretch for 50 minutes was an effective method of elongating tissues.(8) Another study looked at stretching human shoulders into external rotation to increase range of motion. They concluded that treatments consisting of three intervals of five minute stretches, with rest periods of 24 to 48 hours between treatments proved to be an effective method of increasing shoulder extensibility.(9) Both studies showed significantly greater gains when heat was used prior to and during stretches.(8,9) Caution must be taken as tissues can be stretched too aggressively as noted when surgeons attempt to lengthen bone through limb lengthening procedures. If the bone is lengthened too quickly, the surrounding fascial/collagenous tissue cannot replicate fast enough resulting in micro-tearing and fibrosis of the fascial layers, significantly impairing the mobility and function of the limb.(10) Stretching duration of three cycles of five minutes, or a static stretch of up to 50 minutes have been shown to be effective for achieving maximal elongation without risk of fibrosis. Heating prior to and during stretching appears to significantly facilitate tissue elongation.

Stretching leads to decreased tissue sensitivity. A study by Corey et. al (2012) showed the positive effects stretching had on rats which had a tissue irritant injected into the subcutaneous tissue of the back.(11) The rats that were exposed to 10 minutes of stretch, twice per day, for 12 days had a significant reduction in skin sensitivity and an improvement in their gait and stride length as compared to the non-stretched controls. It is unclear whether the decreased sensitivity is at the tissue level or whether it is a central desensitization phenomena. Perhaps the rats were no longer afraid to move in normal ways having been repeatedly stretched into their end ranges of motion. Whichever mechanism is at play, the treatment of a prolonged stretch, without causing pain at the elbow, can be the desensitizing stimulus that down regulates the pain response and allows pain-free return to functional activity.

Tissue tension can be used as the stimulus to elicit healing. In chronic lateral epicondylitis, the common extensor tendon is made up of densely packed fibroblasts, disorganized immature collagen, and an absence of inflammatory cells.(12) Fibroblasts account for approximately 20% of the tissue volume of a tendon.(13) Mechanically stressing fibroblasts leads to increased connective tissue synthesis and decreased production of inflammatory mediators.(14) Mechanical stimulation to fibroblasts in vitro, as shown growing skin cultures, has been shown to align both the extracellular matrix and cytoskeleton components in the direction of the tension leading to increased tensile strength.(15) A gentle stretch could be used as the physiotherapeutic technique to activate the fibroblasts to produce collagen oriented in the direction of the stress. Stretching has the potential to speed healing and increase the extensibility of the tissue resulting in a quicker return to work or sport. Patients that simply rest or protectively splint their arms may not be providing the necessary stimulus to elicit repair of the damaged tendon tissue.

Treatment Parameters

The rationale for the “Armlock” technique is based on sound anatomical and biomechanical principles. Clinically, when performing this stretch, I provide a comfortable level of tension to the tendons so that the patient feels it on the back of the wrist or forearm, but not so strong as to elicit pain at the elbow. One study suggests that three periods of five minutes may be adequate to increase the extensibility of the wrist/finger extensors.(9) However, research on fibroblast cellular activity suggests that the amount of tension is not as important as the duration of the tension.(16) This leads us to conclude that a gentle stretch of 50 minutes may be the more effective treatment strategy. Stretching for 50 minutes a day provides a strong cellular stimulus and allows the rest of the day for the tissue to respond to that stimulus.

Use of this stretching technique, as with any physiotherapy intervention, has to be appropriately based on clinical assessment. First of all, there has to be a demonstrated restriction in range of motion. There are some patients with tennis elbow that have full extensibility of their muscles and therefore would not benefit from this technique. You would simply be stretching joint capsules, and this is not the intent. I do not recommend this treatment to the exclusion of other treatments that currently exist. The Armlock technique should simply be considered another tool in the toolbox to treat this difficult condition.